Perform sanity check on uptime for status page

[Computroniks]

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Description

Commit message:
Fixes #2628
A sanity check is performed when calculating the uptime of a monitor on status page. If it is greater than 100%, we just show 100%. This hasn't been implemented on the dashboard at the request of @louislam due to concerns it would make debugging more difficult in future if changes were made to the uptime calculation.

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• User interface (UI)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods)
• My changes generate no new warnings